On Tuesday, Kamala Harris made her choice for the next vice president of the United States: Gov. Tim Walz of Minnesota. The question is, will this make voters more likely to choose Harris for president in November?
In short: Probably so, but not by much and perhaps not for the reasons you think.
Many people assume that the vice presidential pick will be an electoral game changer. It’s a common mistake: Conventional wisdom has told them that a good one can boost the ticket by several points — and a bad one can sink the campaign. But we’ve spent more than a decade studying candidates for vice president, and our research shows that voters’ opinions of running mates do not have much direct effect on presidential voting.
Even if Walz proves to be quite popular with the American people — or quite unpopular, as Donald Trump’s running mate, JD Vance, has so far proved to be — that in itself won’t change many votes. The fact is, voters are electing a president of the United States first and foremost. Yes, they’re electing a vice president too, but that is much less important to them.
Another common misconception is that a running mate will “deliver” his or her state’s electoral votes for the presidential candidate. It is probably no coincidence that many of the finalists for Harris’ ticket came from electorally competitive states — including Walz. But our research found there is very little evidence of a “home state advantage” for running mates. On average, the effect is close to zero. This makes us skeptical that adding Walz to the ticket somehow guarantees that Democrats will win Minnesota or other competitive Midwestern states.
Walz wouldn’t be to blame for failing to deliver a decisive electoral advantage — nor would Vance, for that matter. Voters just don’t care about running mates quite that much. But the person at the bottom of the ticket can help at the margins, and for good reason: The choice of a vice president tells voters something important about the person running for president.
In the case of Harris, this “first presidential act” tells voters a lot. Americans don’t know her as well as they do Joe Biden or Trump, and she has significantly less time than most presidential candidates to make her case. Her choice will help voters assess her judgment. It also helps them determine whether she makes responsible decisions, for the good of the country, or acts irresponsibly to achieve short-term political gain. It tells people what core political values and priorities guide her.
By picking Walz, Harris has chosen a vice president who is well-qualified for the job. The two-term governor previously served six terms in Congress, where he was the ranking member of the House Veterans’ Affairs Committee. Among Harris’ finalists, he is the only one to have served in state and federal office. Walz’s combination of executive and foreign policy experience — plus his 24 years of service in the Army National Guard — distinguishes him as a plausible “second in command” in a Harris White House.
Voters are likely to reward Harris for choosing a credible potential vice president (and president). In fact, according to our research, this is voters’ most important criterion when evaluating a vice presidential pick. Meeting this test improves voters’ opinions of a presidential candidate’s judgment, which in turn gains them votes.
The opposite is also true. Take the 2008 election, for example. Our analysis showed that voters who doubted Sarah Palin’s readiness to be president lost confidence in John McCain’s judgment and became less likely to vote for the Republican ticket. Conversely, Barack Obama’s selection of Biden — a senator with decades more experience than he had — increased confidence in his acumen and delivered votes to the Democratic ticket. If voters likewise believe that Walz is White House material, he could help Harris win the election.
The choice could also benefit Democrats by reassuring their party’s progressive base of support. Harris was once rated the most liberal member of the Senate, and voters see her as more liberal than Biden. But during the 2020 presidential primaries she was challenged from the left, particularly on her record as a prosecutor and attorney general, and the Biden administration has often faced resistance from more progressive elements of the Democratic Party.
Our research shows that Biden’s selection of Harris for vice president shifted perceptions of his ideology to the left. Walz’s selection could also help frame Harris’ ideology, by reassuring Democrats of her progressive bona fides without alienating more moderate voters. While Walz has governed Minnesota as a progressive, in Congress he represented a Republican-leaning district and was known as a relative moderate.
Voters will determine in November whether Harris made the right decision. For now, we can rely only on evidence from past elections to evaluate her choice. That information suggests we should not expect Walz (or Vance) to be the deciding factor in the election. But if — as we suspect — voters see Walz as a credible potential vice president who can help Harris advance her legislative agenda, he may help her reach the Oval Office.
Christopher J. Devine is an associate professor of political science at the University of Dayton. Kyle C. Kopko is an adjunct professor of political science at Elizabethtown College. Their most recent book is “Do Running Mates Matter? The Influence of Vice Presidential Candidates in Presidential Elections.”
